Many past Tips
have illustrated dimensioning from and to center lines.
There continues to be questions about when it is okay to
dimension with center lines and when it is not
appropriate. Dimensions may be to and from center lines
on a drawing if the dimensions are basic and the center
line is representing the:

axis, center point
or centerplane of a feature of size

center of a pattern
such as a bolt pattern

center of a
radius

center of a slot
length or width

In all of these
cases if direct tolerancing is used, confusion may
result. There is no reason to have this confusion except
to fall back on "that's the way we've always done it".
If you always do what you've always done, you'll always
get what you've always got. In other words, you will
never improve. The drawing below shows the common
correct application of dimensions to center lines. In
every case the dimensions to and from the center lines
are basic.